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Title: Biological control of take-all and Rhizoctonia root rot of wheat by the cyclic lipopeptide-producing strain Pseudomonas fluorescens HC1-07

item YANG, MINGMING - Washington State University
item WEN, SHAN-SHAN - Washington State University
item MAVRODI, DMITRI - Washington State University
item MAVRODI, OLGA - Washington State University
item VON WETTSTEIN, DITER - Washington State University
item Thomashow, Linda
item GUO, JIAN-HUA - Nanjing Agricultural University
item Weller, David

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/14/2013
Publication Date: 3/1/2014
Citation: Yang, M., Wen, S., Mavrodi, D.V., Mavrodi, O.V., Von Wettstein, D., Thomashow, L.S., Guo, J., Weller, D.M. 2014. Biological control of take-all and Rhizoctonia root rot of wheat by the cyclic lipopeptide-producing strain Pseudomonas fluorescens HC1-07. Phytopathology. 104:248-256.

Interpretive Summary: Biological control is the application or stimulation of antagonistic microorganisms for the control of plant pathogens. Some of the most effective biocontrol agents of soilborne pathogens are Pseudomonas bacteria that produce antifungal metabolites such as antibiotics and cyclic lipopeptides (biosurfactants). Take-all and Rhizoctonia root rot are two of the most important root disease of wheat worldwide and there is no resistance in commercial varieties and chemical treatments are only effective during the seedling phase of the diseases. Biological control is the best alternative for controlling these diseases. In this study, we demonstrated that a Pseudomonas strain isolated from wheat provided good control of both take-all and Rhizoctonia root rot when the bacteria were applied as a seed treatment. Further analysis demonstrated that the biocontrol activity resulted from the production of a cyclic lipopeptide which is highly inhibitory to the fungal pathogens that cause these diseases. This research is important because it shows the exact mechanism by which disease is suppressed and it identified an excellent candidate for development into a commercial biocontrol agent.

Technical Abstract: Pseudomonas fluorescens HC1-07, isolated from the phyllosphere of wheat grown in Hebei province, China, inhibited a broad range of plant pathogens, including Gaeumannomyces graminis var. tritici and Rhizoctonia solani AG-8, and suppressed the soilborne diseases of wheat, take-all and Rhizoctonia root rot. Strain HC1-07 produced a cyclic lipopeptide (CLP) with a molecular weight of 1126.42 based on analysis by electrospray ionization mass spectrometry (ESI-MS). Extracted CLP inhibited the growth of G. graminis var. tritici and R. solani in vitro. To determine the role of this CLP in biocontrol, plasposon mutagenesis was used to generate two non-producing mutants, HC1-07viscB and HC1-07prtR2. Analysis of regions flanking plasposon insertions in HC1-07prtR2 and HC1-07viscB revealed that the inactivated genes were similar to prtR and viscB, respectively, of the well-described biocontrol strain P. fluorescens SBW25 that produces the CLP viscosin. Both genes in HC1-07 were required for the production of the viscosin-like CLP. The mutants HC1-07prtR2 and HC1-07viscB were less inhibitory to G. graminis var. tritici and R. solani in vitro, and reduced in ability to suppress take-all as compared to the wild type. HC1-07viscB was reduced in ability to suppress Rhizoctonia root rot. Besides CLP production, prtR also played a role in protease production and colonization of the wheat rhizosphere.